The  Influence  of  Temperature,  Pressure 
and  Supporting  Material  for  the  Cata- 
lyst on  the  Adsorption  of  Gases 
by  Nickel 


ALFRED  WILLIAM  GAUGER 


The  Influence  of  Temperature,  Pressure 
and  Supporting  Material  for  the  Cata- 
lyst on  the  Adsorption  of  Gases 
by  Nickel 


A   DISSERTATION 


PRESENTED  TO  THE 


FACULTY  OF  PRINCETON  UNIVERSITY 

IN  CANDIDACY  FOR  THE  DEGREE 

OF  DOCTOR  OF  PHILOSOPHY 


BY 


ALFRED  WILLIAM  GAUGER 


THE  INFLUENCE  OF  TEMPERATURE,  PRESSURE  AND 

SUPPORTING  MATERIAL  FOR  THE  CATALYST  ON  THE 

ADSORPTION  OF  GASES  BY  NICKEL 

The  importance  of  the  determination  of  the  adsorptive  power  of  catalytic 
materials  for  various  reaction  processes  has  previously  been  emphasized 
and  the  results  accruing  from  a  preliminary  experimental  investigation  of 
a  number  of  metallic  hydrogenation  catalysts  have  already  been  published 
by  Taylor  and  Burns.1  The  results  suggested  that  the  adsorption  obtained 
with  a  given  catalyst  might  be  largely  dependent  on  the  method  of  prepara- 
1  (a)  Taylor,  /.  2nd.  Eng.  Chem.,  13,  75  (1921).  (b)  Taylor  and  Burns,  /.  Am. 
Chem.  Soc.,  43,  1277  (1921). 


rr  o  I  »)O  /I 


tion  and  treatment  accorded  to  the  metal  prior  to  the  experiments.  Fur- 
thermore, the  variability  of  adsorption  with  pressure  in  the  adsorption  of 
hydrogen  by  nickel  as  measured  in  the  earlier  work  seemed  to  indicate 
differences  from  results  obtained  with  adsorbents  of  the  type  of  charcoal. 
The  different  susceptibilities  of  catalytic  agents  to  heat  treatment  when 
spread  on  support  material  and,  alternatively,  when  unsupported,  sug- 
gested also  that  the  adsorptive  capacities  of  catalysts  on  suitable  supports 
should  be  studied.  The  present  work  presents  such  a  study  dealing  in- 
tensively with  nickel  as  a  catalyst  and  with  hydrogen  as  the  adsorbed  gas 
mainly  employed. 

Apparatus  and  Manipulation. — The  apparatus  was  essentially  the 
same  as  that  used  by  Taylor  and  Burns.  A  manometer  was  connected 
to  the  adsorption  bulb  for  the  pressure  measurements.  The  gas  buret 
employed  to  measure  the  gas  recovered  from  the  absorption  bulb  by 
evacuation  through  the  Topler  pump  was  graduated  to  0.01  cc.  The 
sample  of  nickel  nitrate  from  which  the  catalyst  was  prepared  was  de- 
hydrated at  low  temperature  in  a  casserole  and  then  placed  in  the  adsorp- 
tion bulb  in  an  electrically  heated  furnace  as  previously  described  by  Taylor 
and  Burns,  where  it  was  completely  denitrated  by  a  current  of  air  at  the 
temperature  of  reduction  and  then  reduced  by  a  slow  stream  of  pure  dry 
hydrogen.  After  reduction  it  was  allowed  to  cool  in  the  stream  of  hydro- 
gen, and  when  the  material  was  cold  the  hydrogen  was  replaced  by  carbon 
dioxide,  the  wide  end  of  the  bulb  quickly  closed  and  the  bulb  sealed  into 
position  in  the  apparatus,  evacuated  and  filled  with  hydrogen  at  300-310° 
to  reduce  any  oxide  formed  during  the  transfer.  After  this  final  reduction, 
the  bulb  was  evacuated  at  300-310°  until  the  amount  of  gas  coming  off  in 
10-minute  intervals  did  not  exceed  6  cu.  mm.  The  heating  of  the  bulb 
for  this  reduction  and  evacuation  was  accomplished  by  means  of  an  electri- 
cal resistance  furnace. 

When  evacuation  was  complete,  the  bulb  was  cooled  to  25°  and  main- 
tained at  that  temperature  by  a  water-bath  raised  about  it.  A  measured 
quantity  of  pure,  dry  hydrogen  was  then  introduced  into  the  bulb  and  the 
pressure  on  the  manometer  recorded  as  soon  as  equilibrium  was  reached. 
Successive  small  amounts  of  the  gas  were  then  pumped  off  and  measured 
in  the  receiving  buret  which  was  calibrated  to  0.002  cc.  After  each  suc- 
cessive volume  was  removed  from  the  bulb,  the  pressure  of  the  gas  re- 
maining was  recorded  as  soon  as  equilibrium  was  attained.  When  zero 
pressure  at  25°  was  reached,  the  temperature  was  raised  to  300-310° 
and  the  rest  of  the  gas  pumped  off  and  measured.  From  the  successive 
volumes  pumped  off  and  the  total  volume,  the  volume  corresponding  to 
each  pressure  recorded  was  calculated.  The  process  was  repeated  at 
80.5°,  184°,  218°  and  305°.  The  free  space  in  the  bulb  was  determined 
at  each  temperature  by  admitting  pure  dry  nitrogen  at  various  pressures 


up  to  atmospheric  and  recording  the  volumes.  This  involves  the  as- 
sumption that  nitrogen  is  not  measurably  adsorbed  by  nickel.  Experi- 
ments with  helium  as  reference  gas  have  justified  this  assumption.  From 
the  difference  between  the  hydrogen  value  at  each  pressure  measured 
and  the  calculated  nitrogen  value  at  that  pressure  the  number  of  cubic 
centimeters  of  hydrogen  adsorbed  by  the  nickel  was  calculated  and  plotted 
against  respective  pressures.  The  values  so  obtained  at  atmospheric  pres- 
sure are  recorded  in  Table  I. 

Preparation  of  Catalysts. — Nickel  A  was  prepared  by  partially  igniting  the  pure 
nitrate  in  a  casserole  over  a  small  flame,  transferring  this  material  to  the  adsorption 
bulb  and  calcining  at  300  °  in  a  stream  of  air.  The  oxide  was  reduced  at  300  °  in  a  stream 
of  pure,  dry  hydrogen  until  the  amount  of  water  absorbed  from  the  effluent  hydrogen 
by  a  weighed  U-tube  containing  anhydrous  calcium  chloride  did  not  exceed  2.5  mg.  in 
an  hour.  This  sample  contained  15  g.  and  was  not  completely  reduced,  since  a  somewhat 
higher  temperature  (420°  according  to  Senderens  and  Aboulenc)2  is  necessary  for  com- 
plete reduction. 

Nickel  B  consisted  of  1  g.  of  nickel  supported  upon  10  g.  of  diatomaceous  earth. 
It  was  prepared  by  soaking  the  support  in  nickel  nitrate  solution,  drying  and  partly 
calcining  at  low  temperature  in  a  casserole.  This  material  was  then  ground  in  a  mortar, 
placed  in  an  adsorption  bulb  and  calcined  at  300°  for  14  hours  with  a  current  of  air 
passing  through.  Owing  to  the  resistance  of  the  material  to  the  passage  of  gas,  it  was 
necessary  to  place  the  furnace  in  a  horizontal  position  instead  of  in  the  vertical  position 
used  in  the  case  of  Nickel  A.  At  300°,  reduction  was  extremely  slow,  having  only  com- 
menced after  passage  of  hydrogen  for  26  hours  as  indicated  by  the  color  change  of  gray 
to  black ;  the  temperature  was  therefore  increased  to  350  °  and  pure,  dry  hydrogen  passed 
through  for  6.5  days  longer.  At  the  end  of  this  time  the  gain  in  weight  of  the  calcium- 
chloride  tube  indicated  1.5  mg.  of  water  taken  from  the  effluent  gas  per  hour. 

Nickel  C  differed  from  Nickel  B  only  in  the  fact  that  it  was  reduced  for  40  minutes 
at  500°.  A  calcium  chloride  tube  through  which  the  exit  gas  was  passed  during  the 
last  15  minutes  of  the  reduction  period  showed  no  gain  in  weight  "at  the  end  of  the  time. 
Nickel  C  consisted  of  1.04  g.  of  nickel  on  9  g.  of  diatomaceous  earth. 

Nickel  D  was  prepared  by  soaking  6.75  g.  of  diatomite  (Non-Pareil)  brick  graded 
between  8-  and  10-mesh  sieves  with  a  solution  of  pure  nickel  nitrate  of  such  concentra- 
tion that  the  resulting  catalyst  contained  10%  of  metallic  nickel.  The  material  was 
then  calcined  in  a  casserole  at  a  low  temperature  and  reduced  in  the  adsorption  bulb 
at  300°  with  pure,  dry  hydrogen. 

Nickel  E  consisted  of  1  g.  of  nickel  supported  on  9  g.  of  diatomite  brick  graded  as 
above.  It  was  made  by  dissolving  the  required  amount  of  pure  nickel  nitrate  in  suffi- 
cient water  so  that  the  brick  just  soaked  up  all  the  solution.  The  excess  moisture  was 
then  evaporated,  the  material  transferred  to  the  adsorption  bulb  and  calcined  at  400° 
in  a  stream  of  air.  The  resulting  oxide  was  reduced  in  a  stream  of  pure,  dry  hydrogen 
between  300°  and  500°  for  25  minutes,  at  the  end  of  which  time  reduction  was  complete. 
The  temperature  was  maintained  at  500°  for  10  minutes. 

All  of  these  catalysts  represent  materials  of  a  high  degree  of  catalytic  activity. 
As  a  criterion  of  their  activity  it  may  be  stated  that  they  would  rea'dily  hydrogenate 
benzene  vapor  at  70°  and  higher  temperatures. 

The  gases  were  prepared  by  methods  similar  to  those  described  by  Taylor  and  Burns 
with  additional  refinements  to  secure  greater  purity. 


2  Senderens  and  Aboulenc,  Bull.  soc.  chim.,  [4]  11,  641  (1912). 


6 


TABI,B  I 
GAS  VOLUMES  ADSORBED  AT  760  MM.  GAS  PRESSURE 


Sam- 
ple      Support 

Wt. 
G. 

Wt.  Ni 
G. 

Cc.  (0-760  mm.)  ad- 
sorbed by  sample 

Cc.  (0-760  mm.)  ad- 
sorbed per  vol.  of  N» 

Gas 

25°     184° 

218° 

305° 

25° 

184° 

218° 

305° 

A 

None 

15.0 

15.0 

H2 

8.7    7.9 

7.0 

5.4 

5.2 

4.7 

4.2 

3.2 

B 

Diat.  earth 

11.0 

1.1 

H2 

6.30  6.15 

5.65 

50.7 

49.8 

46.3 

C 

Diat.  earth 

10.4 

1.0 

H2 

5.70  5.60 

5.35 

50.7 

49.8 

47.2 

.. 

C02 

..     1.8 

16.0 

- 

E 

Diatomite 

10.0 

1.0 

H2 

4.8       .. 

... 

42.7 

• 

175°  200° 

225° 

250° 

175° 

200° 

225° 

250° 

D 

Diatomite 

7.5 

0.75 

H2 

3.8    3.9 

. 

3.5 

46.3 

45.4 

42.1 

C02 
CO 

1.3     1.2 
5.25 

1.1 

.9 

15.1 

50  4 

14.2 

13.4 

11.8 

Comparison  of  the  results  for  Nickel  A  with  those  of  Taylor  and  Burns 
illustrates  the  fact  that  the  previous  history  of  the  sample  may  have  no 
little  effect  upon  the  capacity  which  it  exhibits  for  adsorbing  hydrogen. 
The  discrepancies  in  the  literature  may  well  be  due  in  part  to  the  treatment 
accorded  the  sample  before  adsorption  measurements  were  made.  These 
have  been  considered  by  Taylor  and  Burns.1  In  this  connection,  it  is  to 
be  noted  that  the  values  given  in  the  tables  represent  a  steady  state  of 
adsorptive  capacity.  The  first  experiment  after  the  reduction  of  Sample 
A  showed  an  adsorption  of  10.4  cc.  at  25°.  The  second  was  at  80.5° 
(see  Fig.  2)  with  a  value  of  9.3  cc.  The  value  of  8.7  cc.  at  25°  is  the  mean 
of  a  number  of  values  ranging  from  8.5  cc.  to  8.9  cc.  obtained  after  num- 
erous experiments  at  different  temperatures.  As  a  check,  a  run  was 
made  at  this  temperature  after  the  final  run  at  305°  and  the  value  of  8.5  cc. 
was  obtained,  which  is  evidence  of  a  steady  adsorptive  capacity. 

The  effect  of  supporting  the  metal  on  an  inert  material  was  to  increase 
its  capacity  for  adsorbing  hydrogen  almost  10-fold,  which  may  be  explained 
on  the  basis  of  increased  effective  surface.  An  additional  advantage  of 
using  a  support  material  such  as  diatomaceous  earth  lies  in  the  fact  that 
the  catalyst  may  be  subjected  to  more  severe  heating  in  the  reduction 
process  without  destruction  of  its  adsorbing  power.  Sample  C  was  main- 
tained at  500°  for  40  minutes  during  the  course  of  reduction,  yet  showed 
practically  the  same  adsorbing  power  as  did  Sample  B  which  was  reduced 
at  350°.  Sample  E  supported  on  diatomite  brick  was  reduced  at  500° 
for  10  minutes  and  showed  an  adsorptive  capacity  only  slightly  less  than 
that  of  Sample  D  on  diatomite  brick  reduced  at  300°.  These  results  are 
in  good  agreement  with  those  of  Kelber  and  of  Armstrong  and  Hilditch3 
who  showed  that  nickel  hydroxide  precipitated  on  diatomaceous  earth 
and  reduced  at  500°  is  an  extremely  active  catalyst.  Taylor  and  Burnslb 
have  shown  that  heating  the  nickel  to  600-700°  decreases  the  adsorption 

3  Kelber,  Ber.t  49,  55,  1868  (1916).     Armstrong  and  Hilditch,  Proc.  Roy.  Soc.,  99A, 
490  (1921). 


between  80  and  97%,  and  Sabatier4  states  that  nickel  reduced  at  700° 
is  practically  inert  as  a  catalyst.  Armstrong  and  Hilditch3  have  shown 
that  ignition  of  an  unsupported  catalyst  at  500°  in  hydrogen  is  sufficient 
to  impair  seriously  its  catalytic  activity.  This  influence  of  the  support 
material  is  of  considerable  importance,  since  complete  reduction  cannot 
be  attained  at  a  temperature  below  420  °.2 

It  is  also  worthy  of  note  that  the  oxide  when  supported  on  diatomaceous 
earth  cannot  be  reduced  at  a  temperature  below  350°  excepting  extremely 
slowly,  whereas  unsupported  nickel  is  rapidly  reduced  at  this  temperature. 
The  explanation  of  this  phenomenon  is  by  no  means  immediately  ap- 
parent. The  molecular  heat  of  formation  of  nickel  oxide  is  59,700  calories. 


mm. 
700 


600 
500 

•S   400 
§ 

£  300 
200 
100 


30S 


O  18*' 


2468  10  cc. 

Cc.  H2  adsorbed  per  15  g.  nickel. 
Fig.  1. 

whereas  the  molecular  heat  of  formation  of  water  vapor  is  58,100  calories; 
the  effect,  therefore,  cannot  be  due  to  local  overheating  in  the  unsupported 
material.  It  would  appear  that  the  reduction  of  nickel  oxide  is  an  inter- 
face phenomenon,  as  has  been  shown  to  be  the  case  for  the  reduction  of 
copper  oxide  by  hydrogen.6  When  the  nickel  oxide  is  spread  over  an  inert 
surface,  the  action  is  probably  much  more  discontinuous  and  more  or  less 

4  Sabatier,  "La  Catalyse  en  Chimie  Organique,"  Libraire  Polytechnique,  Ch. 
Beranger,  Editeur,  1920,  p.  134. 

•  Pease  and  Taylor,  /.  Am.  Chem.  Soc.,  43,  2188  (1921). 


limited  to  two  dimensions,  whereas  in  the  case  of  massive  nickel  oxide  the 
spread  of  reduction  may  take  place  in  every  direction  throughout  the  mass, 
and  therefore  reduction,  under  a  given  set  of  conditions,  will  be  much  more 
rapid  in  the  latter  case  than  in  the  former.  Whether  other  factors  con- 
tribute to  this  anomalous  behavior  is  worthy  of  further  experimental  in- 
vestigation. 

The  Adsorption  Isotherms  of  Hydrogen  on  Nickel 

The  influence  of  pressure  on  the  adsorption  of  hydrogen  by  Sample  A 
was  studied  at  temperatures  of  25°,  80.5°,  184°,  2186  and  305°.  In  Figs. 
1  and  2,  the  volumes  of  gas  in  cubic  centimeters  at  0°-760  mm.  are  plotted 
against  the  pressures  at  the  several  temperatures  studied.  The  curves 
show  the  characteristic 
shape  of  normal  adsorption 
isotherms  with  no  discon- 
tinuities indicative  of  com- 
pound formation  but  with 
the  distinction  that  at  cer- 
tain pressures  a  definite  sat- 
uration capacity  is  reached 
at  each  temperature.  The 
difference  is  apparent  in 
Fig.  2  where  Curve  I  shows 
the  adsorption  isotherm  of 
hydrogen  on  nickel  at  80.5°, 
Curve  II  the  type  (not 
drawn  to  scale)  of  curve  ob- 
tained in  the  case  of  the  dis- 
sociation of  a  salt  hydrate, 
and  Curve  III  represents 
the  adsorption  isotherm  of 
hydrogen  on  charcoal  at  0  ° 
taken  from  results  of  Titoff . 6 
As  Bancroft7  has  pointed 
out,  curves  of  the  type 


Cc.  H2  adsorbed  per  15  g.  nickel. 
Fig.  2. 


shown  in  Fig.  1  represent  either  a  continuous  series  of  solid  solutions  or  ad- 
sorption. Arguments  for  the  latter  are  the  rapidity  with  which  equilibrium 
is  reached  and  the  fact  that  the  action  does  not  follow  Henry's  law.  It 
is  also  to  be  noted  that  the  influence  of  surface  is  further  indication  that 
adsorption  is  involved. 

«  Titoff,  Z.  physik.  Chem.,  74,  64  (1910). 

7  W.  D.  Bancroft,  "Applied  Colloid  Chemistry,"  McGraw-Hill  Book  Co..  Inc., 
New  York,  1921,  p.  34. 


9 


,  The  adsorptive  capacity  is  not  independent  of  temperature,  for  a  different 
saturation  value  or  limit  exists  at  each  temperature.  The  effect  of  in- 
creased temperature  is  to  lower  the  saturation  value,  which  means  that 
the  number  of  spaces  which  can  be  occupied  by  gas*  molecules  is  less  at 
high  temperatures  than  at  low.  Why  this  should  be  the  case  is  by  no 
means  obvious.  The  increased  kinetic  energy  of  some  of  the  surface 
molecules  may  be  so  great,  due  to  the  temperature  increase,  that  all  the 
hydrogen  atoms  striking  the  surface  cannot  remain  thereon  even  momen- 
tarily. This  would  point  to  different  adsorptive  activities  of  individual 
atoms  in  the  metal  surface,  a  conclusion  for  which  we  have  support  from  other 
experimental  studies. 

Discussion  of  the  Isotherms  and  Calculation  of  the  Heat  of  Adsorption 

of  Hydrogen  on  Nickel 

Studies  of  the  influence  of  pressure  on  the  adsorption  of  hydrogen  by 
adsorbents  such  as  charcoal  and  the  zeolite,  chabazite,  have  indicated 
that  the  amount  of  hydrogen  adsorbed  increased  continuously  with  pressure 


mm 
700 

600 
500 
400 
300 
200 
100 


fc 


per   o.t  C. 


6  8 

Cc.  H2  adsorbed. 
Fig.  3. 


10  cc. 


with  no  evidence  of  a  limiting  or  saturation  value.  The  results  obtained 
by  Titoff 6  for  hydrogen  on  charcoal  (Curve  I)  and  by  Seeliger8  for  hydrogen 
on  chabazite  (Curve  II)  are  shown  graphically  in  Fig.  3,  along  with  one  of 
the  isotherms  for  hydrogen  on  nickel  (Curve  III)  for  purposes  of  compari- 
son. The  striking  feature  is  that  a  definite  saturation  capacity  exists  at 
each  temperature  in  the  case  of  hydrogen  on  nickel.  At  this  saturation 
pressure  (P),  nickel  saturated  with  hydrogen  is  in  equilibrium  with  hydro- 
8  Seeliger,  Physik.  Z.,  22,  563  (1921). 


10 

gen  at  pressure  P  and  for  comparison  of  the  isotherms  at  different  tempera- 
tures, P  may  be  taken  as  a  corresponding  condition.  The  condition  is 
one  of  equilibrium;  therefore,  plotting  the  logarithm  of  the  saturation 
pressure  against  the  reciprocal  of  the  absolute  temperature  should  give  a 
straight  line.  These  pressures  were  selected  as  closely  as  is  possible  from 
the  data  and,  thus  plotted,  gave  a  good  approximation  to  a  straight  line. 

We  may  relate  the  variation  of  the  saturation  pressure  to  the  absolute 
temperature  by  means  of  the  Clapeyron  equation  and  thus  calculate  the 
heat  of  evaporation  of  adsorbed  hydrogen  from  the  nickel  surface 


-  — 

d  T     ~  RT*  1V 

where  P  is  the  saturation  pressure  in  mm.  of  mercury;  T,  the  absolute  tem- 
perature; X,  the  heat  of  evaporation  per  gram-molecule,  and  R  is  the  gas 
constant  in  calories,  =  1.99.  Integrating  Equation  1  and  passing  to  Briggs- 
ian  logarithms, 

X  =  1.99  X  2.303    <rr'r*     log  f?  (2) 

1  a  —  1  1         f\ 

the  following  table  indicates  values  of  X  obtained  by  the  use  of  different  pairs 
of  saturation  pressures  and  the  corresponding  temperatures. 


Ti  Tt  Xaai,.  Ti  T»  X^],,.  Ti  T9  XCEie. 

0  C.         °  C.          Cal.  •  C.  °  C.          Cal.  °  C.  °  C.  Cal. 

80  25  2410  184   80    1720  218    184   3590 

184  25  2025  218   80   2076  305    184   3300 

218  25  2200  305   80   2382  305   218   3200 

305  25  2385  .......  ........ 

Av.  value   2529 

The  heat  of  evaporation  and,  therefore,  the  heat  of  adsorption  of  hydro- 
gen on  nickel  given  by  this  method  is  approximately  2500  calories.  This 
value  was  also  obtained  from  the  slope  of  the  curve  in  the  plot  of  the  log- 
arithm of  saturation  pressures  against  reciprocal  of  absolute  temperature. 

Rideal9  has  recently  studied  the  velocity  of  the  following  reaction,  C^H.4 
+  H2  =  C^He,  in  the  presence  of  nickel  catalyst.  Assuming  that  the  rate 
of  reaction  in  the  presence  of  traces  of  oxygen  is  proportional  to  the  rate 
of  evaporation  of  hydrogen  from  the  surface,  he  has  plotted  the  velocity 
against  the  reciprocal  of  the  absolute  temperature  and  obtained  a  straight 
line.  From  the  slope  of  the  curve,  Rideal  calculates  the  heat  of  evaporation 
of  hydrogen  from  the  nickel  surface  to  be  equal  to  12,000  calories  per  gram- 
molecule.  It  may  be  observed  that  the  value  obtained  by  Rideal  is  de- 
pendent on  several  assumptions  with  regard  to  the  mechanism  of  the 
hydrogenation  of  ethylene  in  presence  of  minute  quantities  of  oxygen 
operating  as  a  poison.  The  deduction  in  this  case,  therefore,  of  the  thermal 
quantity  involved  in  the  evaporation  of  hydrogen  from  the  nickel  surface 
•  Rideal,  J.  Chem.  Soc.,  121,  309  (1922). 


11 

is  less  direct  than  our  own.  The  magnitude  of  the  divergence,  however, 
and  the  importance  of  this  quantity  in  the  theory  of  the  subject  warrant  a 
more  direct  determination  of  the  heat  of  adsorption.  This  is  being  at- 
tempted in  this  Laboratory.  There  are  manifest  difficulties  in  the  per- 
formance of  the  experiment.  It  is  of  interest  to  record  that  recent  cal- 
culations of  Bucken10  of  the  work  necessary  to  remove  a  film  of  adsorbed 
hydrogen  from  the  surface  of  charcoal  gave  a  value  of  2500  calories,  and  in 
the  case  of  other  adsorbed  gases  similar  low  values  were  obtained. 

Summary 

1.  Adsorption  isotherms  of  hydrogen  on  nickel  have  been  determined 
using  nitrogen  as  reference  gas. 

2.  A  definite  saturation  capacity  of  nickel  for  hydrogen  exists,  depend- 
ent upon  the  temperature. 

3.  From  the  variation  of  the  saturation  pressure  with  temperature  the 
heat  of  adsorption  of  hydrogen  on  nickel  has  been  calculated  to  be  approxi- 
mately 2500  calories.     Other  methods  of  calculation  give  a  value  of  12,000 
calories.     A  direct  determination  is  being  attempted. 

4.  The  effect  of  using  an  inert  material  for  catalyst  support  has  been 
found  to  increase  greatly  the  adsorptive  capacity  per  gram  of  nickel  and  to 
yield  a  catalyst  that  will  stand  much  more  severe  heat  treatment  without 
diminution  of  its  adsorbing  power. 

I  wish  to  express  my  appreciation  to  Professor  Hugh  S.  Taylor  for  the 
interest  and  advice  given  to  me  in  the  course  of  this  investigation. 
10  Eucken,  Z.  Elektrochem.,  28,  1  (1922). 


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